import math

x1,y1,x2,y2=map(float,input().split())
dis2=(x1-x2)**2+(y1-y2)**2

dis = math.sqrt(dis2)
print('{:.8f}'.format(dis)) import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 dis2=(x1-x2)**2+(y1-y2)**2 dis2 (x1-x2)**2+(y1-y2)**2 (x1-x2)**2 x1-x2 x1 x2 2 (y1-y2)**2 y1-y2 y1 y2 2 dis = math.sqrt(dis2) dis math.sqrt(dis2) math.sqrt math sqrt dis2 print('{:.8f}'.format(dis)) print '{:.8f}'.format(dis) '{:.8f}'.format '{:.8f}' format dis y1,x2,y2=map(float,input().split()) map(float,input().split()) y1 dis2=(x1-x2)**2+(y1-y2)**2 (x1-x2)**2+(y1-y2)**2 dis2 y2=map(float,input().split()) map(float,input().split()) y2 x2,y2=map(float,input().split()) map(float,input().split()) x2 x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 dis = math.sqrt(dis2) math.sqrt(dis2) dis
import math

x1,y1,x2,y2=map(float,input().split())
dis2=(x1-x2)**2+(y1-y2)**2

dis = math.sqrt(dis2)
print('{:.8f}'.format(dis))
